Manta Rays Dive Deep, Don't Flee Storms

Giant reef manta rays inhabiting Papua New Guinea's coastal waters exhibit surprising behavior during monsoon seasons. Previously, scientists believed these creatures migrated to calmer seas when storms hit. However, recent research published in PLOS One indicates that these manta rays simply retreat to deeper ocean environments instead of leaving the area.

Lead researcher Anna Knochel's team tagged ten adult manta rays with satellite trackers between 2016 and 2018 in the Samarai Islands. The study tracked their movements during both the northwest and southeast monsoon seasons. Contrary to expectations of long-distance travel, the tagged rays predominantly stayed within a six-mile radius, with the maximum recorded horizontal movement being just over 50 miles.

These manta rays significantly increased their vertical movements, diving deeper during the monsoons. Average depths reached approximately 207 feet during the northwest monsoon and 161 feet during the southeast monsoon. This diving behavior is directly linked to the concentration of their zooplankton food source, which shifts with ocean productivity during different monsoon periods.

The consistent presence of manta rays in the Samarai Islands area, an upwelling zone in the Coral Sea, means their food is readily available. This eliminates the need for them to undertake extensive migrations. Conservationists emphasize that knowing these animals remain closely associated with specific habitats is crucial for developing targeted protection measures for this vulnerable species.